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class="sidebar-heading"><span>ES6</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Vue</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Vue3</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>React</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Webpack</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Node.js</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>性能优化</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>手写代码</span> <span class="arrow right"></span></p> <!----></section></li></ul> </aside> <main class="page"> <div class="theme-default-content content__default"><h1 id="数组的常用方法"><a href="#数组的常用方法" class="header-anchor">#</a> 数组的常用方法</h1> <ul><li><a href="https://www.runoob.com/typescript/ts-array.html" target="_blank" rel="noopener noreferrer">Array 常用方法<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul> <p>--|--|--|--
序号    |方法   |描述   |实例
1   |concat()   |连接两个或更多的数组，并返回结果。 |[1,2].concat([3,4]) // [1,2,3,4]
2   |every()    |检测数值元素的每个元素是否都符合条件。 |var passed = [12, 5, 8, 130, 44].every(isBigEnough)
3   |filter()   |检测数值元素，并返回符合条件所有元素的数组。
4   |forEach()  |数组每个元素都执行一次回调函数。
5   |indexOf()  |搜索数组中的元素，并返回它所在的位置。如果搜索不到，返回值 -1，代表没有此项。
6   |join()     |把数组的所有元素放入一个字符串。
7   |lastIndexOf()  |返回一个指定的字符串值最后出现的位置，在一个字符串中的指定位置从后向前搜索。
8   |map()  |通过指定函数处理数组的每个元素，并返回处理后的数组。
9   |pop()  |删除数组的最后一个元素并返回删除的元素。
10   |push()    |向数组的末尾添加一个或更多元素，并返回新的长度。
11   |reduce()  |将数组元素计算为一个值（从左到右）。
12   |reduceRight() |将数组元素计算为一个值（从右到左）。
13   |reverse() |反转数组的元素顺序。
14   |shift()   |删除并返回数组的第一个元素。
15   |slice()   |选取数组的的一部分，并返回一个新数组。
16   |some()    |检测数组元素中是否有元素符合指定条件。
17   |sort()    |对数组的元素进行排序。
18   |splice()  |从数组中添加或删除元素。
19   |toString()    |把数组转换为字符串，并返回结果。
20   |unshift() |向数组的开头添加一个或更多元素，并返回新的长度。</p> <h2 id="一、操作方法"><a href="#一、操作方法" class="header-anchor">#</a> 一、操作方法</h2> <p>数组基本操作可以归纳为 增、删、改、查，需要留意的是哪些方法会对原数组产生影响，哪些方法不会</p> <p>下面对数组常用的操作方法做一个归纳</p> <h3 id="增"><a href="#增" class="header-anchor">#</a> 增</h3> <p>下面前三种是对原数组产生影响的增添方法，第四种则不会对原数组产生影响</p> <ul><li>push()</li> <li>unshift()</li> <li>splice()</li> <li>concat()</li></ul> <h4 id="push"><a href="#push" class="header-anchor">#</a> push()</h4> <p><code>push()</code>方法接收任意数量的参数，并将它们添加到数组末尾，返回数组的最新长度</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">;</span> <span class="token comment">// 创建一个数组</span>
<span class="token keyword">let</span> count <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">push</span><span class="token punctuation">(</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 推入两项</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>count<span class="token punctuation">)</span> <span class="token comment">// 2</span>
</code></pre></div><h4 id="unshift"><a href="#unshift" class="header-anchor">#</a> unshift()</h4> <p>unshift()在数组开头添加任意多个值，然后返回新的数组长度</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Array</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 创建一个数组</span>
<span class="token keyword">let</span> count <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">unshift</span><span class="token punctuation">(</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 从数组开头推入两项</span>
<span class="token function">alert</span><span class="token punctuation">(</span>count<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 2</span>
</code></pre></div><h4 id="splice"><a href="#splice" class="header-anchor">#</a> splice</h4> <p>传入三个参数，分别是开始位置、0（要删除的元素数量）、插入的元素，返回空数组</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;blue&quot;</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> removed <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">splice</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token string">&quot;yellow&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;orange&quot;</span><span class="token punctuation">)</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors<span class="token punctuation">)</span> <span class="token comment">// red,yellow,orange,green,blue</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>removed<span class="token punctuation">)</span> <span class="token comment">// []</span>
</code></pre></div><h4 id="concat"><a href="#concat" class="header-anchor">#</a> concat()</h4> <p>首先会创建一个当前数组的副本，然后再把它的参数添加到副本末尾，最后返回这个新构建的数组，不会影响原始数组</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;blue&quot;</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> colors2 <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">concat</span><span class="token punctuation">(</span><span class="token string">&quot;yellow&quot;</span><span class="token punctuation">,</span> <span class="token punctuation">[</span><span class="token string">&quot;black&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;brown&quot;</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// [&quot;red&quot;, &quot;green&quot;,&quot;blue&quot;]</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors2<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// [&quot;red&quot;, &quot;green&quot;, &quot;blue&quot;, &quot;yellow&quot;, &quot;black&quot;, &quot;brown&quot;]</span>
</code></pre></div><h3 id="删"><a href="#删" class="header-anchor">#</a> 删</h3> <p>下面三种都会影响原数组，最后一项不影响原数组：</p> <ul><li>pop()</li> <li>shift()</li> <li>splice()</li> <li>slice()</li></ul> <h4 id="pop"><a href="#pop" class="header-anchor">#</a> pop()</h4> <p><code>pop()</code> 方法用于删除数组的最后一项，同时减少数组的<code>length</code> 值，返回被删除的项</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">]</span>
<span class="token keyword">let</span> item <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">pop</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 取得最后一项</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>item<span class="token punctuation">)</span> <span class="token comment">// green</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors<span class="token punctuation">.</span>length<span class="token punctuation">)</span> <span class="token comment">// 1</span>
</code></pre></div><h4 id="shift"><a href="#shift" class="header-anchor">#</a> shift()</h4> <p><code>shift()</code>方法用于删除数组的第一项，同时减少数组的<code>length</code> 值，返回被删除的项</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">]</span>
<span class="token keyword">let</span> item <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">shift</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 取得第一项</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>item<span class="token punctuation">)</span> <span class="token comment">// red</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors<span class="token punctuation">.</span>length<span class="token punctuation">)</span> <span class="token comment">// 1</span>
</code></pre></div><h4 id="splice-2"><a href="#splice-2" class="header-anchor">#</a> splice()</h4> <p>传入两个参数，分别是开始位置，删除元素的数量，返回包含删除元素的数组</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;blue&quot;</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> removed <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">splice</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 删除第一项</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// green,blue</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>removed<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// red，只有一个元素的数组</span>
</code></pre></div><h3 id="slice"><a href="#slice" class="header-anchor">#</a> slice()</h3> <p>slice() 用于创建一个包含原有数组中一个或多个元素的新数组，不会影响原始数组</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;blue&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;yellow&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;purple&quot;</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> colors2 <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">slice</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> colors3 <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">slice</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors<span class="token punctuation">)</span>   <span class="token comment">// red,green,blue,yellow,purple</span>
concole<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors2<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// green,blue,yellow,purple</span>
concole<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors3<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// green,blue,yellow</span>
</code></pre></div><h4 id="改"><a href="#改" class="header-anchor">#</a> 改</h4> <p>即修改原来数组的内容，常用<code>splice</code></p> <h5 id="splice-3"><a href="#splice-3" class="header-anchor">#</a> splice()</h5> <p>传入三个参数，分别是开始位置，要删除元素的数量，要插入的任意多个元素，返回删除元素的数组，对原数组产生影响</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;blue&quot;</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> removed <span class="token operator">=</span> colors<span class="token punctuation">.</span><span class="token function">splice</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;purple&quot;</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 插入两个值，删除一个元素</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>colors<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// red,red,purple,blue</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>removed<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// green，只有一个元素的数组</span>
</code></pre></div><h4 id="查"><a href="#查" class="header-anchor">#</a> 查</h4> <p>即查找元素，返回元素坐标或者元素值</p> <ul><li>indexOf()</li> <li>includes()</li> <li>find()</li></ul> <h5 id="indexof"><a href="#indexof" class="header-anchor">#</a> indexOf()</h5> <p>返回要查找的元素在数组中的位置，如果没找到则返回 -1</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> numbers <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
numbers<span class="token punctuation">.</span><span class="token function">indexOf</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">)</span> <span class="token comment">// 3</span>
</code></pre></div><h5 id="includes"><a href="#includes" class="header-anchor">#</a> includes()</h5> <p>返回要查找的元素在数组中的位置，找到返回<code>true</code>，否则<code>false</code></p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> numbers <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
numbers<span class="token punctuation">.</span><span class="token function">includes</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">)</span> <span class="token comment">// true</span>
</code></pre></div><h5 id="find"><a href="#find" class="header-anchor">#</a> find()</h5> <p>返回第一个匹配的元素</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">const</span> people <span class="token operator">=</span> <span class="token punctuation">[</span>
    <span class="token punctuation">{</span>
        name<span class="token operator">:</span> <span class="token string">&quot;Matt&quot;</span><span class="token punctuation">,</span>
        age<span class="token operator">:</span> <span class="token number">27</span>
    <span class="token punctuation">}</span><span class="token punctuation">,</span>
    <span class="token punctuation">{</span>
        name<span class="token operator">:</span> <span class="token string">&quot;Nicholas&quot;</span><span class="token punctuation">,</span>
        age<span class="token operator">:</span> <span class="token number">29</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">]</span><span class="token punctuation">;</span>
people<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">element<span class="token punctuation">,</span> index<span class="token punctuation">,</span> array</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> element<span class="token punctuation">.</span>age <span class="token operator">&lt;</span> <span class="token number">28</span><span class="token punctuation">)</span> <span class="token comment">// // {name: &quot;Matt&quot;, age: 27}</span>
</code></pre></div><h2 id="二、排序方法"><a href="#二、排序方法" class="header-anchor">#</a> 二、排序方法</h2> <p>数组有两个方法可以用来对元素重新排序：</p> <ul><li>reverse()</li> <li>sort()</li></ul> <h3 id="reverse"><a href="#reverse" class="header-anchor">#</a> reverse()</h3> <p>顾名思义，将数组元素方向反转</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> values <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
values<span class="token punctuation">.</span><span class="token function">reverse</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">alert</span><span class="token punctuation">(</span>values<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 5,4,3,2,1</span>
</code></pre></div><h3 id="sort"><a href="#sort" class="header-anchor">#</a> sort()</h3> <p>sort()方法接受一个比较函数，用于判断哪个值应该排在前面</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">compare</span><span class="token punctuation">(</span><span class="token parameter">value1<span class="token punctuation">,</span> value2</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>value1 <span class="token operator">&lt;</span> value2<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">return</span> <span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>value1 <span class="token operator">&gt;</span> value2<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">return</span> <span class="token number">1</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
        <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token keyword">let</span> values <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">10</span><span class="token punctuation">,</span> <span class="token number">15</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
values<span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span>compare<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">alert</span><span class="token punctuation">(</span>values<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 0,1,5,10,15</span>
</code></pre></div><h2 id="三、转换方法"><a href="#三、转换方法" class="header-anchor">#</a> 三、转换方法</h2> <p>常见的转换方法有：</p> <h3 id="join"><a href="#join" class="header-anchor">#</a> join()</h3> <p>join() 方法接收一个参数，即字符串分隔符，返回包含所有项的字符串</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> colors <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token string">&quot;red&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;green&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;blue&quot;</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token function">alert</span><span class="token punctuation">(</span>colors<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token string">&quot;,&quot;</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// red,green,blue</span>
<span class="token function">alert</span><span class="token punctuation">(</span>colors<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token string">&quot;||&quot;</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// red||green||blue</span>
</code></pre></div><h2 id="四、迭代方法"><a href="#四、迭代方法" class="header-anchor">#</a> 四、迭代方法</h2> <p>常用来迭代数组的方法（都不改变原数组）有如下：</p> <ul><li>some()</li> <li>every()</li> <li>forEach()</li> <li>filter()</li> <li>map()</li></ul> <h3 id="some"><a href="#some" class="header-anchor">#</a> some()</h3> <p>对数组每一项都运行传入的函数，如果有一项函数返回 true ，则这个方法返回 true</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> numbers <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> someResult <span class="token operator">=</span> numbers<span class="token punctuation">.</span><span class="token function">some</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">item<span class="token punctuation">,</span> index<span class="token punctuation">,</span> array</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> item <span class="token operator">&gt;</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>someResult<span class="token punctuation">)</span> <span class="token comment">// true</span>
</code></pre></div><h3 id="every"><a href="#every" class="header-anchor">#</a> every()</h3> <p>对数组每一项都运行传入的函数，如果对每一项函数都返回 true ，则这个方法返回 true</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> numbers <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> everyResult <span class="token operator">=</span> numbers<span class="token punctuation">.</span><span class="token function">every</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">item<span class="token punctuation">,</span> index<span class="token punctuation">,</span> array</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> item <span class="token operator">&gt;</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>everyResult<span class="token punctuation">)</span> <span class="token comment">// false</span>
</code></pre></div><h3 id="foreach"><a href="#foreach" class="header-anchor">#</a> forEach()</h3> <p>对数组每一项都运行传入的函数，没有返回值</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> numbers <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
numbers<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">item<span class="token punctuation">,</span> index<span class="token punctuation">,</span> array</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
    <span class="token comment">// 执行某些操作</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre></div><h3 id="filter"><a href="#filter" class="header-anchor">#</a> filter()</h3> <p>对数组每一项都运行传入的函数，函数返回 <code>true</code> 的项会组成数组之后返回</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> numbers <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> filterResult <span class="token operator">=</span> numbers<span class="token punctuation">.</span><span class="token function">filter</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">item<span class="token punctuation">,</span> index<span class="token punctuation">,</span> array</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> item <span class="token operator">&gt;</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>filterResult<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 3,4,5,4,3</span>
</code></pre></div><h3 id="map"><a href="#map" class="header-anchor">#</a> map()</h3> <p>对数组每一项都运行传入的函数，返回由每次函数调用的结果构成的数组</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">let</span> numbers <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">let</span> mapResult <span class="token operator">=</span> numbers<span class="token punctuation">.</span><span class="token function">map</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">item<span class="token punctuation">,</span> index<span class="token punctuation">,</span> array</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> item <span class="token operator">*</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>mapResult<span class="token punctuation">)</span> <span class="token comment">// 2,4,6,8,10,8,6,4,2</span>
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